1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to motion estimation in an image pickup apparatus, and more particularly, to estimating a global motion vector of an image due to hand trembling by using zoom information and focus information.
2. Description of the Related Art
Most moving picture processing techniques use a motion compensation approach to estimate only a motion of a local object appearing between neighboring frames. This motion is referred to as a local motion. However, in actual moving pictures, motion in addition to the local motion, such as a zoom motion, a pan motion, and rotation of a camera, affects the whole image. This motion affecting the whole image is referred to as global motion. In general, an image pickup device such as a camera or a camcorder uses a global motion detection method to adjust the position of a frame.
In such an image pickup device, the spatial position of an image changes over time due to hand trembling and nearby vibrations.
In general, in an image obtained through a moving camera, the motion of the background and the motion of an object exist at the same time, and therefore the global motion is calculated in each image, thereby detecting the motion of the object.
In a related art method of estimating a global motion vector, it is difficult to find a global motion vector because of a zoom magnification provided by an image pickup device.
FIG. 1A illustrates an image photographed when a magnification is small and FIG. 1B illustrates an image photographed when the magnification is larger.
When hand trembling and motion of an object occur at the same time, the motion of the object can be found in an object area 103 illustrated in FIG. 1A.
In this case, motion due to hand trembling also appears in an area outside the object image area 103.
However, if the zoom magnification becomes larger as illustrated in FIG. 1B, the object image area 104 becomes relatively larger with respect to the whole area 102.
Accordingly, the motion of the object has a frequency less than that of the camera intended by a user manipulating the camera, but with the increasing zoom magnification, the motion of the object becomes an increasing portion of the whole image.
As a result, if the zoom magnification increases, the motion of the object increasingly affects the whole image, thereby causing a problem in selecting a global motion vector due to hand trembling.